Lubricating oil process



Nov. 1-3, 1934.

v. VOORHEES El AL LUBRICATING OIL PROCESS File d June so. 1932 W II a b QEQ N R8 m E M WM- N w W 93 63. wmww U r N kuog N3 .BRRER mmm m m-N NO WM It a 0 NW Q fiw k 1 N OJY NN Mm B RQQQE Patented Nov. 13, 1934 UNITED STATES PATENT OFFICE LUBRICATING OIL PROCESS Indiana Application June so, 1932, Serial No. 620,192

13 Claims.

This invention relates to a process of producing high quality lubricating oils from mineral oil lubricating distillates of intermediate quality. One of the objects of the invention is to provide a means of separating frommixed base lubricating oils, parafiinic fractions having low viscosity temperature susceptibility. Another object of the invention is to produce lubricating oils of high resistance to sludge formation. Still another object of the invention is to provide a process for separating lubricating fractions of high viscosity index, high sludge stability and low pour test from unrefined lubricating distillates of intermediate viscosity index and high wax content without the use of chemical treating agents (except for finishing) and without the production of noisome byproducts. Other objects of the invention will become apparent as the description proceeds.

Most petroleum oils, and particularly paraffin and. mixed-base petroleum oils, contain substantial quantities of paraffin wax which accumulates in the lubricating oil fractions obtained on distillation. Thus Mid-Continent lubricating distillates may contain 10% of paraflin wax and Salt Creek lubricating distillates will contain as much as 20% of wax. For most lubricating purposes it is necessary to remove this wax before the oil will suitably fulfill the requirements met in use. The principal objection to the presence of wax in lubricating oils is the effect of the wax on the pour test of the oil. A very small amount of wax, as little as 1 will greatly increase the pour test, the increase in some oils amounting to as much as 20 to 25 F. For oils which are required to flow freely at low temperatures, for example, motor oils used for the lubrication of automobiles in winter service, it is necessary to remove practically all of the parafiin wax which they naturally contain.

40 When the wax is removed from the oil, however,

there occurs a pronounced change in the viscosity.

of the oil and particularly in the viscosity temperature characteristics. The susceptibility to change in viscosity with temperature is always increased and this is in general a very undesirable result. Accordingly, completely dewaxed mixedbase oils are, in general, inferior in this respect to oils which contain substantial quantities of wax and. have a higher pour test. Where the oil is destined for use at higher temperatures, therefore, it is advantageous to refine the oil in such a way as to allow a substantial proportion of the wax to remain in it, for the reason that the oil so produced will better withstand high temperatures and better retain its viscosity under severe (Cl. 196-13)v conditions to lubrication. There is, however, a serious objection to allowing any substantial quantity of wax to remain in the oil because of difliculties which may result in case abnormally low temperatures are encountered. By the pres- SJ ent invention we have been able to produce a lubricating oil with properties resembling those of parafiin wax and yet substantially free from the objectionable property of high pour test. Briefly 1 described, our invention is as follows: A lubricating distillate, which may suitably have a viscosity of from 200 to 3000 Saybolt at F. and. which may be derivedfrom any suitable mineral oil, but particularly from mixed base crude petroleum, is mixed and diluted under i pressure with a liquid of high fluidity, preferably a liquefied gas which is a solvent for the oil and chemically inert thereto; For this purpose we prefer to use liquefied hydrocarbons and particularly liquid ethane, but other suitable gases may be employed, such as butane, propane, methane, ethylene, acetylene and the like. Gases other than hydrocarbons may also be employed, such as ethyl chloride, dichlordifluor methane, methylene fluoride, and dimethyl ether. Mixtures of gases may likewise be used and we may employ mixtures of liquefied gases and normally liquid solvents, for example, hexane, or ethyl ether. Varying proportions of oil and diluent may be employed but in general we prefer to use from 2 to 10 volumes of diluent per volume of oil, depending on the viscosity of the oil and also the nature of the diluent. The first step after obtaining the solution of oil and liquefied gaseous diluent is to effect a preliminary separation of substances undesirable in the finished product. If the oil being treated is wholly unrefined and contaminated with appreciable quantities of aspha'ltic matter, a preliminary separation maybe made at normal temperature, e. g. 50100 F. When liquid ethane is employed most of the asphaltic matter will precipitate at a temperature of 80 F. under a pressure of about 610 pounds per square inch. The separated liquid may then be cooled to a relatively low temperature to precipitate the paraflin wax which it contains, as previously referred to, unless the oil is substantially wax free as is the case with oils from certain crudes such as Winkler County crude. It is, of course, unnecessary to make a preliminary separation of asphalt, unless desired for special reasons. The paraffin wax may be separated at a temperature between zero and -'50 F. and this temperature will depend largely on the nature of the diluent and, the, completeness with which wax separation is desired. The low temperature necessary for wax separation may be obtained most conveniently by self-refrigeration, allowing a controlled portion of the diluent to evaporate from the solution, butit should be understood that any other cooling means may be employed. The wax which separates may suitably be precipitated from the solution by gravity, or the solution may be passed through a filter where the wax is removed as a cake and separately freed from the oil and diluent.

The oil solution now freed from paraffin wax is now subjected to conditions of extreme refrigeration at temperatures of the order of -80 to 200 F. We have discovered that when lubricating oils are subjected to these extremely low temperatures in the presence of suitable diluents,

particularly liquefied hydrocarbon gases, a remarkable phenomenon takes place. Hydrocarbons which have heretofore been considered to be uncrystallizable are converted into crystalline deposits with properties somewhat similar to those possessed by paraffin wax at ordinary temperatures. A substantial portion of the oil may be crystallized in this fashion and from a Mid- Continent S. A. E. 50 distillate we have been able to separate over 20% of a lubricating oil fraction with new and valuable properties. Our process differs from those processes heretofore employed in that we separate from lubricating oils an oil fraction-having improved viscosity stability characteristics, whereas previous processes have almost invariably separated from the oil fractions having less desirable characteristics than those of the hydrocarbons remaining.

The intermediate crystalline fraction which separates from the oil at extremelylow temperatures can be removed by any suitable method, such as settling, centrifuging or filtration. After separation from the oil the desired crystalline material may be subjected to a washing step and the freed from diluent by heating. The oil remaining in solution may be recovered by evaporation of the diluent or itmay be cooled to a still lower temperature for the separation of a second fraction of desirable crystalline material.

In the accompanying drawing, which forms a part of this specification, I have diagrammatically shown a plant for continuously treating lubricating oil according to the above procedure.

Referring to the drawing, lubricating oil is introduced by line 1- and pump 2 to mixer 3 where it is mixed with liquid ethane from diluent storage tank 4 conducted to the mixer by line 5. From mixer 3 the solution is passed through valve 6 into settler 7. 'Here the pressure is reduced by withdrawing vapors through valve 8 and the temperature is allowed to fall to approximately 40 F. At this temperature substantially all the paraffin wax precipitates in the base of settler 7 and the clearsolution is withdrawn from the upper part of the settler through line 9. Perforated baffle 10 assists in carrying out the quite separation of the solid from the liquid. The oil passing. through line 9 suffers a second reduction of pressure at valve 11 where it enters settler 12.

Vapors are also removed from this chamber by a suitable valve 13 and the temperature of the solution is thereby reduced. Operating in this manner there is no difficulty in obtaining a temperature as low as ,110 F. when liquid ethane is employedas the diluent. At this temperature a considerable proportion of the oil is crystallized and precipitates in the ,base of settler 12. Supernatant oil. flows through line 14 and heat exchanger 15 to stripping drum 16. A further reduction of pressure may take place on entering the stripping drum, depending on the character of conducting the last stage of the chilling process. Normally, however, pressurein ,thestripper will be approximately the same-as that in the settler 12. Vapors released from the stripper are passed by line 17 to gas collecting main 18 and thence to compressor 19 where they are recompressed and liquefied in condenser 20 and returned to diluent storage tank 4. Condensation may be facilitated by circulating a suitable liquid heat carrying medium between heat exchanger 15 and condenser 20. The refrigeration available in heat exchanger 15 may also be used to precool the diluent flowing through line 5 before entering mixer 3. Various other refrigeration economies may be effected but these have been omitted in the interest of simplification and clarity. Lower temperatures may be obtained by applying a partial vacuum .to settler 12.

Heat may be supplied to the stripper 16 by a closed steam coil or by an open steam pipe 21, as illustrated. The oil recovered from the final solution is discharged by valve 22 and line 23. Paraflin wax which accumulates in the bottom of settler 7 is passed through valve 24 and line 25 to stripper 26 where it is melted by steam supplied throughline27. The ethane is driven off. through line 28 to gas main 18 for recovery and v the residual wax is discharged through valve 29 and line 30. Any asphaltic matter which has not been previously removed from the oil will usuallyv where it is freed from diluent by the application of heat, or by a current of steam introduced by. line 34. The diluent vapors arev discharged by.

line 35 and the desired oil is discharged from the base of the stripper by valve '36 in line 37., This oil may suitably be subjected to a further refining treatment, such as a light treatment with sulfuric acid and/or filtration through fuller.s earth. v

' Diluent which may inadvertently .be lost from the system is replaced .byintroducing additional quantities through line 38 into the diluent storage tank 4. Water which is added to the system as steam or otherwise, collects in the base of the diluent storage tank and is periodically .withdrawn through line 39 and valve 40. If desired, the wax fraction obtained fromthebase of settler 12 may be transferred to a separate tank where it is washed with precooled diluent to more completely remove the oily fraction. All low temperature apparatus is of course thoroughly heat insulated. I

As an example ofthe results obtainable byour process, a Mid-Continent lubricating distillate having a viscosity of 1114 at 100 F. and 88 at 210 F. (viscosity index 85 as calculated, by the method of Dean and Davis Chem. 8: Met. Eng. 1929, vol. 36, page 618) was dewaxed to produce an oil having a pour testj ofv 0f F. This all was diluted with 5 volumes of liquid propane and cooled to a temperature of -105 F. by indirect refrigeration withsolid carbon dioxide. A pre cipitate wasobtained whichv was substantially. freed from diluent and exhibited a viscosity of 69 seconds Saybolt at 210? F. and 539 seconds Saybolt at 100? F. ,corresponding .to a viscosity index of 108. This oil had a solid point of about +30 F., and a yield of about 20% was obtained.

Although the solid point of this oil was not very low, by more completely dewaxing the original oil, a lower pour test could be obtained for the finished product.

We have described our invention in connection with certain specific examples thereof, but intend that its scope shall be defined by the following claims interpreted as broadly as the art will permit.

We claim:

1. The process of separating from substantially wax free mineral lubricating oils, 2. paraflinic fraction having a lower viscosity temperature coefficient than the oil treated, comprising diluting the oil with a solvent of high fluidity, refrigerating the solution to a temperature below that required to separate wax, whereby said parafiinic oil fraction is crystallized, separating said crystallized oil fraction from the remaining solution, discarding the oil remaining in solution and recovering and melting the crystallized oil fraction.

2. The process according to claim 1 wherein the solution of oil and solvent isrefrigerated to a temperature between 50 and 200 F.

3. The process according to claim 1 wherein the solution of oil and solvent is refrigerated to a temperature between 100 and 200 F.

4. The process according to claim 1 wherein the solvent employed for diluting the oil is a liquefied gas.

5. The process according to claim 1 wherein the solvent employed for diluting the oil is a liquefied normally gaseous hydrocarbon.

6. The process of separating from mineral lubricating oils fractions having lower viscosity temperature coefiicients than the oil treated, comprising diluting the oil with a solvent of high fluidity, subjecting the solution to a preliminary dewaxing treatment by refrigerating to a sufficiently low temperature to separate the wax from the solution, further refrigerating the solution to a lower temperature than required to separate wax, whereby a parafiinic oil fraction is crystallized, separating the crystallized fraction from the remaining solution, discarding the oil remaining in solution and recovering and melting the crystallized fraction.

7. The process according to claim 6 wherein the solution of oil and solvent is refrigerated to a temperature between 50 and -200 F.

8. The process according to claim 6 wherein the solution of oil and solvent is refrigerated to a temperature between 100 and 200 F.

9. The process according to claim 6 wherein the solvent employed for dilutingthe oil is a liquefied gas.

10. The process according to claim 6 wherein the solvent employed for diluting the oil is a liquefied normally gaseous hydrocarbon.

11. The process according to claim 6 wherein the solvent employed is a liquefied normally gaseous hydrocarbon and the solution is subjected to a preliminary refining treatment, comprising separating at normaltemperatures an insoluble asphaltic fraction.

12.-The process of separating from wax-free mixed-base petroleum lubricating oils fractions more paraffinic than the oil treated, comprising diluting the oil under superatmospheric pressure with a liquefied normally gaseous hydrocarbon, 1o expanding and evaporating a portion of the dim-X ent, whereby the temperature is reduced between 80 and 200 F. and a parafiinic oil fraction is crystallized, separating the said paraflinic oil fraction from theremaining solution and recov- 1m ering and melting the crystallized fraction.

13. The process according to claim 12 wherein the diluent is liquid ethane.

VANDERVEER vooRrn'rEs. JOHN A. ANDERSON. 

